Abstract: A new parabolic ultrasonic transformer is developed. Based on wave equation of longitudinal vibration of variable cross-section rod,the wave equation and parameter formulas of the parabolic horn are derived. A design of the parabolic horn with the same frequency and different area ratio as well as the modal analysis has been done,and the resonant frequency is determined using finite element method. It is shown that this kind of ultrasonic horn is better in form factor and amplitude amplification factor than other types of horns,and that the simulation result is consistent with the theoretical analysis.